PtPd/CeO₂ catalytic enhanced WO₃ nanofibers bilayer gas sensor for ppb-level xylene detection

Long-term exposure to xylene can seriously damage the respiratory and central nervous systems. Xylene poses significant health risks even at trace levels in the ppb range, highlighting the need for the ppb-level detection. Designing high-performance gas-sensitive materials and sensing structures is essential to address high operating temperatures and poor trace detection. In this work, PtPd nanobimetallic-sensitized CeO₂ porous nanospheres were prepared as the upper catalytic layer via solution self-assembly and impregnation, with WO₃ nanofibers as the lower sensing layer to form a bilayer sensor. The 1 wt%Pt₇₀Pd₃₀/CeO₂/WO₃ sensor showed the best response (R_a/R_g = 38.67) to 10 ppm xylene at 180℃, and it demonstrates a obvious response to xylene at ultra-low concentrations down to 1 ppb (R_a/R_g = 1.4). The sensor also exhibits good stability and notable humidity resistance. By combining in-situ infrared and online mass spectrometry, we show that xylene is catalytically converted into toluene and methyl radicals upon passing through the 1 wt% Pt₇₀Pd₃₀/CeO₂ layer, significantly enhancing response performance. In summary, the novel bilayer sensor developed in this study enables trace xylene detection at the ppb level and shows potential for environmental monitoring applications.